Apparatus and method for producing hologram and apparatus and method for displaying hologram

Abstract

Used as a propagation function is a half-plane propagation function which is restricted such that it has a value only within a half plane in a predetermined direction perpendicular to a propagating axis in a plane which is perpendicular to the propagating axis. According to a convolution integration with this function, the wavefront of object light on a hologram surface is determined, whereby hologram data is produced. Thus produced hologram is read out by means of readout light. After the light with a wavefront forming the conjugate image of the object to be viewed is blocked, the image of the object to be viewed is observed. Thus, a hologram, which has a high quality and from which the conjugate image is easily eliminated at the time of image reproduction, is produced while a recording device with a relatively low spatial resolution is used, and a three-dimensional form is displayed while the distortion with respect to the original image is reduced in thus produced hologram and the conjugate image is eliminated therefrom.

What is claimed is: 
     
       1. A hologram calculating apparatus, for calculating desired hologram data displayed on a hologram surface of an in-line type hologram display apparatus to project a hologram image, comprising: a wavefront determining section for determining a wavefront O of object light at a position of said hologram image in response to a given optical virtual image to be only observed, said hologram image being magnified with an imaging optical system of said hologram display; and   a data calculating section for calculating said desired hologram data by computing a wavefront u of the object light at said hologram surface including performing a convolution integration of a propagation function f and an initial wavefront O of the object light at said hologram image.   
     
     
       2. A hologram calculating apparatus according to claim 1, wherein said wavefront determining section comprises: a position computing section for computing a position of said hologram image based on characteristics of said imaging optical system; and   a wavefront computing section for computing said wavefront O of the object light at said hologram image.   
     
     
       3. A hologram calculating apparatus according to claim 1, wherein said wavefront determining section comprises: a position computing section for computing positions on said hologram surface, each position of said positions on said hologram surface corresponding to a selected point on said optical virtual image based on characteristics of said imaging optical system; and   a wavefront computing section for computing wavefronts of the object light at each point of said hologram image.   
     
     
       4. A hologram calculating apparatus according to claim 1, further comprising a region defining section for defining said propagation function f of the wavefront at said hologram surface within a predetermined half plane in response to a mask of said imaging optical system which only passes light forming said optical virtual image. 
     
     
       5. A hologram calculating apparatus according to claim 4, wherein said data calculating section calculates said desired hologram data by calculating only a real component of said wavefront u of the object light at said hologram surface. 
     
     
       6. A hologram calculating method, for calculating desired hologram data projected on a hologram surface of an in-line type hologram display to project a hologram image, comprising: determining a wavefront O of object light at a position of said hologram image in response to a given optical virtual image to be observed, said hologram image being magnified with an imaging optical system of said hologram display; and   calculating said desired hologram data by computing a wavefront u of object light at said hologram surface including performing a convolution integration of a propagation function f and an initial wavefront O of the object light at said hologram image.   
     
     
       7. A hologram calculating method according to claim 6, wherein said determining a wavefront comprises: computing a position of said hologram image based on characteristics of said imaging optical system; and   computing said wavefront O of the object light at said hologram image.   
     
     
       8. A hologram producing method according to claim 6, wherein said determining a wavefront comprises: computing positions on said hologram surface, each position of said positions on said hologram surface corresponding to a selected point on said optical virtual image based on characteristics of said imaging optical system; and   computing wavefronts of the object light at each point of said hologram image.   
     
     
       9. A hologram calculating method according to claim 6, further comprising defining said propagation function f of the wavefront at said hologram surface within a predetermined half plane in response to a mask of said imaging optical system which only passes light forming said optical virtual image. 
     
     
       10. A hologram calculating method according to claim 9, wherein said calculating said desired hologram data is calculating only a real component of said wavefront u of the object light at said hologram surface. 
     
     
       11. An in-line type hologram display apparatus for displaying a hologram image with given hologram data, comprising: a hologram surface for displaying said given hologram data to project a hologram image; and   an imaging optical system for magnifying said hologram image to produce an optical virtual image.   
     
     
       12. A hologram display apparatus according to claim 11, wherein said hologram surface is a part of a spatial light modulator. 
     
     
       13. A hologram display apparatus according to claim 12, further comprising: a light source to generate a readout light for said spatial light modulator.   
     
     
       14. A hologram display apparatus according to claim 11, further comprising: a mask disposed at a focal point position of said imaging optical system opposite to said hologram image so as to only pass light forming said optical virtual image.   
     
     
       15. A hologram display method for displaying a hologram with given hologram data, comprising: projecting a hologram image by displaying said given hologram data on a hologram surface; and   producing an optical virtual image by magnifying said hologram image with an imaging optical system.   
     
     
       16. A hologram display method according to claim 15, further comprising: passing only light forming said optical virtual image through a focal point position of said imaging optical system opposite to said hologram image.   
     
     
       17. An in-line type hologram producing apparatus, comprising: a hologram surface for displaying hologram data to project a hologram image;   an imaging optical system for magnifying said hologram image to produce an optical virtual image;   a wavefront determining section for determining a wavefront O of object light at a position of said hologram image in response to said optical virtual image; and   a data calculating section for calculating said hologram data by computing a wavefront u of object light at said hologram surface including performing a convolution integration of a propagation function f and an initial wavefront O of the object light at said hologram image.   
     
     
       18. An in-line type hologram producing apparatus according to claim 17, wherein said wavefront determining section comprises: a position computing section for computing a position of said hologram image based on characteristics of said imaging optical system; and   a wavefront computing section for computing said wavefront O of the object light at said hologram image.   
     
     
       19. An in-line type hologram producing apparatus according to claim 17, wherein said wavefront determining section comprises: a position computing section for computing positions on said hologram surface, each position of said positions on said hologram surface corresponding to a selected point on said optical virtual image based on characteristics of said imaging optical system; and   a wavefront computing section for computing wavefronts of the object light at each point of said hologram image.   
     
     
       20. An in-line type hologram producing apparatus according to claim 17, further comprising: a mask disposed at a focal point position of said imaging optical system opposite to said hologram image so as to only pass light forming said optical virtual image.